1. Field of the Invention
This invention relates to graphene, and in particular to large area uniformly or substantially uniformly doped graphene.
2. Description of Related Art
The doping of graphene, for example to enhance its electrical properties, reducing its electrical resistance, or alter other properties thereof, is known. By way of example, a method is described in Adv. Mat. 24, 2844 (2012) (I Khrapach, et al.) by which small chips of flakes of graphene may be doped with iron (III) chloride. The method involves placing the small chips or flakes of graphene and iron (III) chloride under low pressure conditions for a period of time during which the graphene and iron (III) chloride are heated. This process may be repeated several times. It has been found that the method produces doped few layer graphene chips or flakes, the graphene layers being intercalated with the iron (III) chloride. The resulting doped product is of considerably reduced electrical resistance compared to pristine graphene chips or flakes, with resistance or resistivity values comparable with the best known transparent conductors.
Whilst the method outlined hereinbefore and described in the I Khrapach, et al., paper produces small doped graphene flakes or chips, it has been found that it is only effective when used with small chips or flakes of graphene. Its use with larger area graphene elements has been found to produce non-uniform doping with the result that the graphene elements so doped would be unsuitable for use in the industrial scale production of, for example, electronic equipment. Accordingly, the I Khrapach method has been found to be of only limited applicability.